While solar power is a promising source of renewable energy, significant challenges remain with respect to exploiting this technology. One such challenge may involve a susceptibility of solar power systems to be influenced by a wide range of operating conditions. This susceptibility in part may stem from the architecture by which solar power systems typically are designed. In particular, solar power systems generally may utilize a distributed architecture, wherein a relatively large number of individual solar sources—such as solar panels—are used to generate power from sunlight. While ultimately the output of these individual solar sources may be combined to produce the overall power put out by the system, nevertheless each individual solar source may operate within its own set of conditions apart from the other solar sources in the system.
Several factors may influence the conditions within which individual solar sources operate. These conditions may include temperature, insolation, the photoelectric characteristics of the solar source itself, and the like. Moreover, individual solar sources frequently are operated with the goal of obtaining the maximum possible power output from the source. Techniques for operating an individual solar source in this manner generally may be referred to as maximum power point tracking (MPPT), and may be described in some embodiments for example in U.S. patent application Ser. No. 12/363,709, Filed Jan. 30, 2009, entitled “Systems for Highly Efficient Solar Power Conversion”; International Patent Application No. PCT/US08/80794, filed Oct. 22, 2008, entitled “High Reliability Power Systems and Solar Power Converters”; International Patent Application No. PCT/US08/79605, filed Oct. 10, 2008, entitled “Novel Solar Power Circuits and Powering Methods”; International Patent Application No. PCT/US08/70506, filed Jul. 18, 2008, entitled “High Efficiency Remotely Controllable Solar Energy System”; International Patent Application No. PCT/US08/60345, filed Apr. 15, 2008, entitled “AC Power Systems for Renewable Electrical Energy”; and International Patent Application No. PCT/US08/57105, filed Mar. 14, 2008, entitled “Systems for Highly Efficient Solar Power”; each hereby incorporated by reference herein in its entirety. As a result of these factors, each solar source in a solar power system may operate within a set of conditions perhaps unique and different from the other solar sources in the system.
Because a typical solar power system may have a large number of individual solar sources, each operating essentially within its own conditional framework, the task of combining the voltage outputs of these various solar sources to achieve a consistent and efficient operating voltage of the solar power system may pose technical challenges. For example, the solar sources in a solar power system often may be interconnected in various serial and parallel structures, such as wherein a number of individual solar panels may be serially connected to form a string, and wherein a number of strings may be connected in parallel to form an array. Naturally, the electrical properties of such serial and parallel connections may affect how the voltage output of individual solar sources is combined with the operating voltage of the overall system.
At one extreme, for example, underperforming solar sources on an individual string may cause a voltage drop in the string as a whole, since the total voltage in the string merely is the sum of the voltages of the individual solar sources on the string due to the serial nature of their interconnection. If the voltage in the string drops below a certain level, this may cause a loss of power for the array of strings connected in parallel, due to their parallel interconnection.
At another extreme, spikes in the output of individual solar sources in a string may cause a voltage gain for the string as whole, which again may result in inefficiencies due to the connection topology. Such spikes in voltage may be undesirable for efficiency, safety, or regulatory reasons. For example, solar power systems often are subject to regulatory requirements that impose a maximum operating voltage for the system—frequently a limit of 600 volts—and spikes in the voltage output of individual solar sources can cause the total voltage in the system to exceed the regulatory limit.
To deal with technical issues of this nature, conventional solar power systems may utilize techniques to limit the voltage output of solar sources. For example, where a solar source is known to put out a certain voltage under normal conditions, limits may be designed to create an operating range encompassing both the source's expected normal output as well as a degree of variance to accommodate changes in operating conditions. One architecture for setting such limits may involve connecting each solar source to a photovoltaic DC-DC power converter, wherein the converter may have hardware or software that sets voltage output limits within which the solar source is permitted to operate, and wherein the converters may be serially connected to form a string. The voltage output limits may provide a voltage output range within which the solar source may operate that can accommodate a degree of changed conditions. Should the voltage output limits be exceeded, the solar source may be shut down, disengaged, or otherwise controlled within the solar power system.
However, conventional voltage output limits for solar sources may entail significant drawbacks. For example, conventional voltage output limits only may be capable of being statically set. Once set, the voltage output limits may not be able to be adjusted in real time with respect to changing conditions affecting the solar power system. As a result, setting conventional voltage output limits in this manner may have resulted in undesirable trade-offs. For example, one trade-off may be to foreclose circumstances where it may be desirable to put out voltage for an individual solar source beyond the limit set for its output, such as perhaps to offset unusual voltage drops elsewhere in the system.
The foregoing problems related to conventional solar power systems may represent a long-felt need for an effective solution to the same. While implementing elements may have been available, actual attempts to meet this need may have been lacking to some degree. This may have been due to a failure of those having ordinary skill in the art to fully appreciate or understand the nature of the problems and challenges involved. As a result of this lack of understanding, attempts to meet these long-felt needs may have failed to effectively solve one or more of the problems or challenges here identified. These attempts may even have led away from the technical directions taken by the present inventive technology and may even result in the achievements of the present inventive technology being considered to some degree an unexpected result of the approach taken by some in the field.